1. Field of the Invention
The present invention relates to compositions and methods for improving insulin sensitivity. Specifically, the invention provides methods for improving insulin sensitivity by using a polysaccharide isolated from Hirsutella sinensis as well as methods for preparing the polysaccharides.
2. The Prior Art
Traditional Chinese medicine has been used for several thousands of years in Asian countries. One class of traditional remedies consists of medicinal mushrooms that include Antrodia cinnamomea, Agaricus blazei Murrill, Ganoderma lucidum, and Ophiocordyceps sinensis. These mushrooms contain a wide range of immuno-modulatory and bioactive compounds. The medicinal mushroom Ophiocordyceps sinensis has a long history of use to promote health and longevity. Recent work has identified that the anamorph (or mycelium) of O. sinensis fruiting bodies is Hirsutella sinensis. Extracts of O. sinensis fruiting bodies and H. sinensis mycelium have been shown to produce various effects on laboratory animals, including showing anti-fatigue, anti-inflammatory, kidney-protecting, and libido-enhancing properties.
Type 2 diabetes mellitus is a disease characterized by abnormal regulation of blood glucose levels. If left uncontrolled for a prolonged period of time, this condition may lead to several complications, including cardiovascular disease, eye damage, foot ulcers, kidney failure, and stroke. In developed countries, the high prevalence of diabetes is currently a major threat to public health, with approximately 387 million diabetic people worldwide. Prevention of diabetes therefore represents a major challenge.
During the early stage of type 2 diabetes, human peripheral tissues, including the liver, muscles, and adipose tissues, show reduced sensitivity to insulin. At this stage, a number of treatments can be used to stabilize blood glucose levels, including diet monitoring, regular exercise, and medications. For example, metformin is a synthetic drug that decreases hyperglycemia by suppressing glucose production by the liver; by increasing sensitivity to insulin in peripheral tissues; and by decreasing absorption of glucose from food. However, metformin and other anti-diabetic medications produce many side-effects that may limit treatment efficacy and patient compliance.
In view of the growing incidence of diabetes in the human population and the difficulties observed with the prevention and treatment of this condition, there is a need for alternative measures to prevent, treat or control this debilitating disease. New measures that can be introduced in the diet without requiring important changes in lifestyle and without producing severe toxicity or adverse effects on health are especially needed.